Background: The impact of patient prosthesis mismatch (PPM) on the outcome after TAVI is a matter of ongoing research. The method to calculate PPM has been subject to several adaptations in order to refine risk stratification. Recently, the conventional way to measure the LVOT-Diameter via echocardiography has been challenged by CT guided LVOT measurements.

Purpose: The aim of this study was to compare TTE vs. CT guided indexed effective orifice area (iEOA) measurements and investigate the impact of conventional versus area and perimeter derived LVOT calculations within the CT dataset for PPM appraisal.

Methods: From our ongoing, prospective single-centre TAVI registry we enrolled 472 patients that received an echocardiographic assessment as well as a pre-TAVI CT before undergoing a TAVI procedure. We calculated LVOT via transthoracic echocardiographic parasternal axis views by using the continuity equation Vmax. The standard pre-TAVI CT was used for LVOT measurements using directly measured diameter, as well as area and perimeter derived diameter. LVOT diameter was measured 4 mm below the annulus in balloon expandable valves and directly below the Valve cage in self expandable valves. All measurements were performed using 3mensio structural heart software ver. 8.0 (Pie Medical Imaging BV). EOA was indexed to Body surface area and cut-offs for PPM severity were adapted to BMI. In patients with BMI<30, moderate PPM was defined as iEOA < 0.85 and severe:< 0.65, while in patients with BMI >=30 moderate PPM meant iEOA <0.7 and severe: <0.55. Comparison between groups was done using the t-test.

Results: Patients were 82 ± 5.7 years old, STS score was 5.2 ± 4.1 and 250 (53%) patients received a self-expandable valve. PPM was diagnosed in 155 (33%) patients via echo derived LVOT. CT derived LVOT using direct measure identified 29 (6,1%) patients with PPM. Area derived LVOT identified 29 (6,1%) patients and perimeter derived LVOT via CT identified 27 (5,7%) patients with PPM. The correlation of iEOA to postinterventional pmean was better when perimeter derived CT LVOT was used, rather than echo derived LVOT (r = -0.49 vs. r = -0.38). Patients receiving a self-expandable valve seemed less often affected by severe PPM. This effect was least pronounced in echo guided LVOT measurement (p= 0.06) and most pronounced in CT guided directly measured LVOT (p=0.01). Days to last follow up were 273 ± 113. A difference in mortality could not be associated with either group.

Conclusion: Prevalence of PPM seems clearly overestimated by echo-based LVOT measurement and is significantly lower by integrating CT derived LVOT measurements in iEOA calculation. Correlation of postinterventional pmean to iEOA was better if CT derived LVOT measurements were used. Self-expandable transthoracic heart valves had significant less PPM when measured by CT. No differences were found in mortality between groups.